Printing by a jet of ink has been disclosed in many of the prior art patents, many of which disclose a system for emitting a stream of ink drops and then selectively, electrostatically deflecting these ink drops to form alphanumeric characters. Such systems are suitable for small size characters of about typewriter size characters but have not been found to emit enough ink to create larger size characters, e.g. three to five centimeters in height. Large rolls of paper, for example, being produced by a paper mill, need labeling information somewhere on the exterior surface, which labeling information includes the name of the manufacturer, the type or grade of the paper, the run number, the weight of the roll, the date, addressee, etc. Typically, this information was hand labeled on the exterior or was hand printed on the exterior or was stenciled onto the exterior or onto a label which was then glued to the exterior surface. A presently commercially available mechanical system for printing of bulk items such as rolls of paper utilizes a constant air supply plus selective valving of ink to nozzles and by this means labels are imprinted. The valving of the ink can lead to potentially serious problems of clogging of the valves with dried ink, particulates, etc. Also the speed of production of the label is limited by the viscosity and density of the fluid. In all of these prior attempts, especially the hand labeling, there was always the problem of illegibility of the label information and there was always the problem with the excess manpower requirements.
In the early development phase valving of ink was an attempt to create metered slug flow of ink interspersed with air but the physical constraints of this type of ink flow prohibited the accurate metering and delivery of ink droplets and therefore the printing achieved by this system was not sufficiently legible.
Accordingly the problem to be solved is how to achieve printing of label information on bulk items such as rolls of paper by printing this information directly on an exterior surface of the roll in large letters or numerals, how to accomplish the printing with speed, ease and a minimum of manpower, and without the necessity of adhesively applying labels to the bulk material.